Browsing by Author "Philbert, Anitha"

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    Farmers’ pesticide usage practices in the malaria endemic region of North-Western Tanzania: implications to the control of malaria vectors
    (BioMed Central (BMC), 2019-11) Philbert, Anitha; Lyantagaye, Slyvester, L; Nkwengulila, Gamba
    Background: Pesticides remain the mainstay for the control of agricultural pests and disease vectors. However, their indiscriminate use in agriculture has led to development of resistance to both crop pests and disease vectors. This threatens to undermine the success gained through the implementation of chemical based vector control programs. We investigated the practices of farmers with regard to pesticide usage in the vegetable growing areas and their impact on susceptibility status of An. gambiae s.l. Methods: A stratified multistage sampling technique using the administrative structure of the Tanzanian districts as sampling frame was used. Wards, villages and then participants with farms where pesticides are applied were purposively recruited at different stages of the process, 100 participants were enrolled in the study. The same villages were used for mosquito larvae sampling from the farms and the surveys were complimented by the entomological study. Larvae were reared in the insectary and the emerging 2–3 days old female adults of Anopheles gambiae s.l were subjected to susceptibility test. Results: Forty eight pesticides of different formulations were used for control of crop and Livestock pests. Pyrethroids were the mostly used class of pesticides (50%) while organophosphates and carbamates were of secondary importance. Over 80% of all farmers applied pesticides in mixed form. Susceptibility test results confirmed high phenotypic resistance among An. gambiae populations against DDT and the pyrethroids (Permethrin-0.75%, Cyfluthrin-0.15%, Deltametrin-0.05% and Lambdacyhalothrin-0.05%) with mortality rates 54, 61, 76 and 71%, respectively. Molecular analysis showed An. arabiensis as a dominant species (86%) while An. gambiae s.s constituted only 6%. The kdr genes were not detected in all of the specimens that survived insecticide exposures. Conclusion: The study found out that there is a common use of pyrethroids in farms, Livestocks as well as in public health. The study also reports high phenotypic resistance among An. gambiae s.l against most of the pyrethroids tested. The preponderance of pyrethroids in agriculture is of public health concern because this is the class of insecticides widely used in vector control programs and this calls for combined integrated pest and vector management (IPVM).
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    Habitat productivity and pyrethroid susceptibility status of Aedes aegypti mosquitoes in Dar es Salaam, Tanzania
    (BioMed Central (BMC), 2017-05) Mathias, Leah; Baraka, Vito; Philbert, Anitha; Innocent, Ester; Francis, Filbert; Nkwengulila, Gamba; Kweka, Eliningaya, J
    Background: Aedes aegypti (Diptera: Culicidae) is the main vector of the dengue virus globally. Dengue vector control is mainly based on reducing the vector population through interventions, which target potential breeding sites. However, in Tanzania, little is known about this vector’s habitat productivity and insecticide susceptibility status to support evidence-based implementation of control measures. The present study aimed at assessing the productivity and susceptibility status of A. aegypti mosquitoes to pyrethroid-based insecticides in Dar es Salaam, Tanzania. Methods: An entomological assessment was conducted between January and July 2015 in six randomly selected wards in Dar es Salaam, Tanzania. Habitat productivity was determined by the number of female adult A. aegypti mosquitoes emerged per square metre. The susceptibility status of adult A. aegypti females after exposure to 0.05% deltamethrin, 0.75% permethrin and 0.05% lambda-cyhalothrin was evaluated using the standard WHO protocols. Mortality rates were recorded after 24 h exposure and the knockdown effect was recorded at the time points of 10, 15, 20, 30, 40, 50 and 60 min to calculate the median knockdown times (KDT50 and KDT95). Results: The results suggest that disposed tyres had the highest productivity, while water storage tanks had the lowest productivity among the breeding habitats Of A. aegypti mosquitoes. All sites demonstrated reduced susceptibility to deltamethrin (0.05%) within 24 h post exposure, with mortalities ranging from 86.3 ± 1.9 (mean ± SD) to 96.8 ± 0.9 (mean ± SD). The lowest and highest susceptibilities were recorded in Mikocheni and Sinza wards, respectively. Similarly, all sites demonstrated reduced susceptibility permethrin (0.75%) ranging from 83.1 ± 2.1% (mean ± SD) to 96.2 ± 0.9% (mean ± SD), in Kipawa and Sinza, respectively. Relatively low mortality rates were observed in relation to lambda-cyhalothrin (0.05%) at all sites, ranging from 83.1 ± 0.7 (mean ± SD) to 86.3 ± 1.4 (mean ± SD). The median KDT50 for deltamethrin, permethrin and lambda-cyhalothrin were 24.9–30. 3 min, 24.3–34.4 min and 26.7–32.8 min, respectively. The KDT95 were 55.2–90.9 min for deltamethrin, 54.3–94. 6 min for permethrin and 64.5–69.2 min for lambda-cyhalothrin. Conclusions: The productive habitats for A. aegypti mosquitoes found in Dar es Salaam were water storage containers, discarded tins and tyres. There was a reduced susceptibility of A. aegypti to and emergence of resistance against pyrethroid-based insecticides. The documented differences in the resistance profiles of A. aegypti mosquitoes warrants regular monitoring the pattern concerning resistance against pyrethroid-based insecticides and define dengue vector control strategies
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    Preferred breeding habitats of Aedes Aegypti (Diptera- Culicidae) Mosquito and its public health implicati ons in Dares Salaam, Tanzania
    (E3 Journals, 2013-11) Philbert, Anitha; Ijumba, Jasper,N
    The larval habitats of the mosquito Aedes aegypti L (Diptera-Culicidae) were investigated in urban Da r es Salaam, using larval traps (old tyres, vegetations, outdoor water storage containers and flower pots). The study was carried out in the four sampling sites namely, Vingunguti, Julius Nyerere International Airport (J NIA), Mbagala and Mkuranga (Vikindu). The aim was to asse ss the influence of habitat changes in urban Dar es Salaam (the capital city of the united republic of Tanzania) on the preferred breeding habitats of Ae. Aegypti mosquitoes and its possible public health implicati ons on the residents of the City. Aedes aegypti mosquitoes bred in all the habitats sampled. Old tyres recorde d the highest number of Ae. aegypti mosquitoes followed by water storage containers and vegetation. Flower-pot s habitat was the least preferred, with the lowest number of Ae. aegypti mosquitoes.Other mosquito species belonging to fiv e genera were also collected and these were found to live in sympatry with Ae. aegypti larvae. Statistical analysis revealed a significan t difference in species occurrence in the four larval habitats sampled. The availability of the habitats to support the breedi ng of Ae. aegypti mosquito, which are potential vectors of urban yel low fever, Chikungunya fever, Dengue fever and Rift Valley Fever Viruses implies that theresidents of D ar es Salaam City are at risk of mosquito-borne dis eases should an outbreak occur. It is therefore important that, residents of the City are enlightened on env ironmental factors that contribute to mosquito breeding and th at, the Government together with the community inst itute proper sanitation measures to reduce mosquito breed ing habitats.
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    Pyrethroids and DDT tolerance of Anopheles gambiae s.l. from Sengerema District, an area of intensive pesticide usage in north-western Tanzania
    (Willey online Library, 2017-04) Philbert, Anitha; Lyantagaye, Slyvester, L; Pradel, Gabriela; Ngwa, Julious, C; Nkwengulila, Gamba
    objective To assess the susceptibility status of malaria vectors to pyrethroids and dichlorodiphenyltrichloroethane (DDT), characterise the mechanisms underlying resistance and evaluate the role of agro-chemical use in resistance selection among malaria vectors in Sengerema agro-ecosystem zone, Tanzania. methods Mosquito larvae were collected from farms and reared to obtain adults. The susceptibility status of An. gambiae s.l. was assessed using WHO bioassay tests to permethrin, deltamethrin, lambdacyhalothrin, etofenprox, cyfluthrin and DDT. Resistant specimens were screened for knockdown resistance gene (kdr), followed by sequencing both Western and Eastern African variants. A gas chromatography–mass spectrophotometer (GC-MS) was used to determine pesticide residues in soil and sediments from mosquitoes’ breeding habitats. results Anopheles gambiae s.l. was resistant to all the insecticides tested. The population of Anopheles gambiae s.l was composed of Anopheles arabiensis by 91%. The East African kdr (L1014S) allele was found in 13 of 305 specimens that survived insecticide exposure, with an allele frequency from 0.9% to 50%. DDTs residues were found in soils at a concentration up to 9.90 ng/g (dry weight). conclusion The observed high resistance levels of An. gambiae s.l., the detection of kdr mutations and pesticide residues in mosquito breeding habitats demonstrate vector resistance mediated by pesticide usage. An integrated intervention through collaboration of agricultural, livestock and vector control units is vital
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    A Review of Agricultural Pesticides Use and the Selection for Resistance to Insecticides in Malaria Vectors
    (Scientific Research, 2014) Philbert, Anitha; Lyantagaye, Sylvester L.; Nkwengulila, Gamba
    Most national malaria control programmes rely extensively on pyrethroid insecticides to control mosquito vectors of this disease. Unfortunately, the intensive use of this class of insecticides both in public health and agriculture has led to its reduced efficacy. The objective of this review was to assess the role of agricultural pesticides use on the development of resistance to insecticides in malaria vectors and the potential impact of this resistance on control activities. We searched library catalogues and public databases for studies that included data on resistance to the major classes of insecticides: organochlorines, carbamates, organophosphates and pyrethroids, in the malaria vectors of Anopheles genera. There is a strong geographical bias in published studies many originating from West African countries. Several studies demonstrate that resistance to pyrethroids is widespread in the major malaria vectors of the Anopheles gambiae and Anopheles funestus complexes. Assessing the impact of insecticide resistance on vector control is complicated owing to the lack of studies into the epidemiological consequences of resistance on the control of malaria and other vector borne diseases.
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    A Review of Agricultural Pesticides Use and the Selection for Resistance to Insecticides in Malaria Vectors
    (Scientific Research, 2014-07) Philbert, Anitha; Lyantagaye, Sylvester Leonard; Nkwengulila, Gamba
    Most national malaria control programmes rely extensively on pyrethroid insecticides to control mosquito vectors of this disease. Unfortunately, the intensive use of this class of insecticides both in public health and agriculture has led to its reduced efficacy. The objective of this review was to assess the role of agricultural pesticides use on the development of resistance to insecticides in malaria vectors and the potential impact of this resistance on control activities. We searched library catalogues and public databases for studies that included data on resistance to the major classes of insecticides: organochlorines, carbamates, organophosphates and pyrethroids, in the malaria vectors of Anopheles genera. There is a strong geographical bias in published studies many originating from West African countries. Several studies demonstrate that resistance to pyrethroids is widespread in the major malaria vectors of the Anopheles gambiae and Anopheles funestus complexes. Assessing the impact of insecticide resistance on vector control is complicated owing to the lack of studies into the epidemiological consequences of resistance on the control of malaria and other vector borne diseases.
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    A zooprophylaxis strategy using l-lactic acid (Abate) to divert host-seeking malaria vectors from human host to treated non-host animals
    (BioMed Central (BMC), 2020-01) Kemibala, Elison, E; Mafra‑Neto, Agenor; Dekker, Teun; Saroli, Jesse; Silva, Rodrigo; Philbert, Anitha; Nghabi, Kija; Mboera, Leonard, E.G
    Background: Zooprophylaxis is a technique in which blood‑seeking vectors are diverted to non‑host animals in order to lower blood‑feeding rates on human hosts. The success of this technique depends on the host preference of the vector being targeted. The objective of this study was to evaluate the efect of l‑lactic acid (Abate) to divert malaria mosquito, Anopheles gambiae from feeding on human host. Methods: A 14‑month‑old female goat was treated with Abate, a formulation incorporating l‑lactic acid into a slow‑ release matrix. This formulation was applied on the fur of the goat’s back and neck. The treated animal was then pre‑ sented to Anopheles gambiae sensu stricto (s.s.) as a prospective host in a semi‑feld environment (‘mosquito sphere’) together with either an untreated animal or a human. The number of mosquitoes caught to each host choice ofered were compared. Results: Goat treated with the l‑lactic acid formulation successfully attracted An. gambiae at higher rates (70.2%) than the untreated ones (29.8%). Furthermore, An. gambiae s.s. were attracted to a treated goat at an equivalent degree (47.3%) as to their preferred human host (52.7%), even when the preferred host was present in the same environment. Conclusions: The fndings indicate that human host‑seeking mosquitoes can be diverted into feeding on non‑ preferred hosts despite the close proximity of their favoured host, hence reducing chances for the transmission of blood‑borne parasites